By the BEKI team currently on Bawean (Mark, Simen, Shafia) When we first talked about the Bawean serpent eagle (Spilornis cheela baweanus; included in the BEKI logo) with our forestry friends here on Bawean, they were surprised. Is this bird endemic to Bawean? We sent out an email to the forestry department in Surabaya on East-Java with some photos we managed to take. To our surprise, we got asked to write an popular article about the Bawean serpent eagle in the monthly forestry bulletin! Great news and a big honour! All of us here at BEKI and the forestry department on Bawean hope that it might help raise awareness for the need of research on this unique and little known raptor.
This is a short English summary of the article that we have written: The most well-known Bawean endemic is the Bawean deer (Axis kuhlii). However, next to this species, there are many other different taxa that are endemic to Bawean island, such as our current focus animal the Bawean warty pig, and the Bawean serpent eagle. All three are included in the BEKI logo. The Bawean serpent eagle is currently treated as a sub-species of the Crested serpent eagle (Spilornis cheela), however, several authors argue that it is an own island species. The species is a medium-sized raptor (approx. 50cm), with a dark brown to blackish head, uniformly brown chest and white spots covering the belly, sides and underparts. (Photo 1 & 2). These white spots are also present on the head and back of the neck- and wings. The head, chest, belly, sides and underparts of juveniles are of a white colour (Photo 3). Furthermore, three small tail bands could still be observed in flight, whereas only two broad tail bands were observed in adults. (Photo 4). The only species specific study on the Bawean serpent eagle was a 15 day survey conducted by Vincent Nijman in 2006, who estimated that 60 -75 pairs are still present on the island with a crude home range of between 3.5 and 6.0 km. He also found that they used tall forest more than expected on the basis of its availability, and coastal forest less than expected. We collected data about the Bawean serpent eagle during 40 days. We took a GPS and noted down details about how many individuals we saw and the age class. In total 43 observations were made in which 67 adult- and 5 juvenile individuals were observed. 60% percent of the observations were single birds, 28% consisted of pairs, 5% of three birds and single observations were made of groups including 4, 5 and 7 birds. Sightings were obtained across all habitat types except marsh forest. Next to this, sightings were mostly concentrated in the middle part of the island and no sightings were obtained in coastal areas. Although our methods are non-systematic, we will continue collecting data, as so little is known about the birds. Reference: Nijman, V. (2006). The endemic Bawean Serpent-eagle Spilornis baweanus: habitat use, abundance and conservation. Bird Conservation International, 16, 131-143.